A steering apparatus for an automobile, as illustrated in FIG. 26, is constructed so that rotation of the steering wheel 1 is transmitted to an input shaft 3 of a steering gear unit 2, and as this input shaft 3 turns, the input shaft 3 pushes or pulls a pair of left and right tie rods 4, which apply a steering angle to the front wheels of the automobile. In order to accomplish this, the steering wheel 1 is fastened to and supported by the rear end section of a steering shaft 5, and this steering shaft 5 is inserted in the axial direction through a cylindrical shaped steering column 6, and is supported by this steering column 6 such that it can rotate freely. The front end section of the steering shaft 5 is connected to the rear end section of an intermediate shaft 8 via a universal joint 7, and the front end section of this intermediate shaft 8 is connected to the input shaft 3 via a different universal joint 9.
Construction for protecting a driver from a collision between the body of the driver and the steering wheel 1 during a collision accident is required in a steering apparatus. For example, by constructing the intermediate shaft 8 so that it can contract over its entire length due to an impact load, then when the steering gear unit 2 is displaced in the backward direction due to a primary collision between an automobile and another automobile or the like, that displacement is absorbed, which prevents the steering wheel 1 from displacing in the backward direction via the steering shaft 5 and hitting the body of the driver.
After the primary collision, a secondary collision occurs when the body of the driver collides with the steering wheel 1. Therefore, the steering apparatus for an automobile also requires construction that allows the steering wheel 1 to displace in the forward direction while absorbing impact energy. As this kind of construction, construction is known (refer to JP51-121929(U) and JP2005-219641(A)) and widely used in which an energy absorbing member, which absorbs an impact load by plastically deforming, is provided between the vehicle body and a member that supports the steering column 6 that supports the steering wheel 1 with respect to the vehicle body so that it can break away in the forward direction due to an impact load in the forward direction during a secondary collision, and displaces in the forward direction together with the steering column 6.
FIG. 27 and FIG. 28 illustrate an example of this kind of steering apparatus. A housing 10, which houses the reduction gear and the like of an electric power steering apparatus, is fastened to the front end section of a steering column 6a. A steering shaft 5a is supported on the inside of the steering column 6a such that it can only rotate freely, and a steering wheel 1 (see FIG. 26) can be fastened to the portion on the rear end section of this steering shaft 5a that protrudes from the opening on the rear end of the steering column 6a. The steering column 6a and the housing 10 are supported by a fastening bracket 11 on the vehicle side (see FIG. 1) that is fastened to the vehicle body so that they can break away in the forward direction due to an impact load in the forward direction.
To accomplish this, a support bracket 12 on the column side that is supported in the middle section of the steering column 6a and a support bracket 13 on the housing side that is supported by the housing 10 are supported with respect to the vehicle body so that they both can break away in the forward direction due to an impact load in the forward direction. These brackets 12, 13 both comprise installation plate sections 14a, 14b at one or two locations, and notch sections 15a, 15b are formed in these installation plate sections 14a, 14b so that they are open on the rear end edges. With these notch sections 15a, 15b covered, sliding plates 16a, 16b are assembled in the portions of the support brackets 12, 13 near both the left and right ends.
These sliding plates 16a, 16b are formed by bending thin metal plate such as carbon steel plate or stainless steel plate provided with a layer of a synthetic resin that slides easily, such as polyamide resin (nylon), polytetrafluoroethylene resin (PTFE) or the like on the surface into a U shape, having a top plate section and a bottom plate section that are connected by a connecting plate section. Through holes for inserting bolts or studs are formed in portions of the top and bottom plate sections that are aligned with each other. With these sliding plates 16a, 16b mounted on the installation plate sections 14a, 14b, the through holes are aligned with the notch sections 15a, 15b that are formed in these installation plate sections 14a, 14b. 
The support brackets 12, 13 are supported by the fastening bracket 11 on the vehicle side by screwing nuts onto bolts or studs that are inserted through the notch sections 15a, 15b in the installation plate sections 14a, 14b and the through holes in the sliding plates 16a, 16b, and tightening the nuts. During a secondary collision, the bolts or studs come out from the notch sections 15a, 15b together with the sliding plates 16a, 16b, which allows the steering column 6a and the housing 10 to displace in the forward direction together with the support brackets 11, 12 and the steering wheel 1.
Moreover, in the example in the figure, energy absorbing members 17 are provided between the bolts or studs and the bracket 12 on the column side. As this bracket 12 on the column side displaces in the forward direction, the energy absorbing members 17 plastically deform so as to absorb the impact energy that is transmitted to the bracket 12 on the column side by way of the steering shaft 5a and steering column 6a. 
During a secondary collision, the bolts or studs come out from the notch sections 15a, which allows the bracket 12 on the column side to displace in the forward direction, and the steering column 6a displaces in the forward direction together with this bracket 12 on the column side. When this happens, the bracket 13 on the housing side also breaks away from the vehicle body, and is allowed to displace in the forward direction. As the bracket 12 on the column side displaces in the forward direction, the energy absorbing members 17 plastically deform and absorb the impact energy that is transmitted from the driver's body to the bracket 12 on the column side by way of the steering shaft 5a and the steering column 6a, which lessens the impact applied to the body of the driver.
In the case of the construction illustrated in FIG. 27 to FIG. 29, the support bracket 12 on the column side is supported by the fastening bracket 11 on the vehicle side at two locations, on both the right and left side, so that it can break away in the forward direction during a secondary collision. From the aspect of stable displacement in the forward direction without causing the steering wheel 1 to tilt, it is important during a secondary collision, that the pair of left and right support sections be disengaged at the same time. However, tuning in order that these support sections disengage at the same time is affected not only by resistance such as the friction resistance and the shear resistance to the disengagement of these support sections, but unbalance on the left and right of the inertial mass of the portion that displaces in the forward direction together with the steering column 6a, so takes time and trouble.
Moreover, in this construction, in the process of the housing 10 displacing in the forward direction together with the steering column 6a as a secondary collision advances, it becomes easy for the vertical position of the rear section of the steering column 6a to change excessively. The reason that it becomes easy for the vertical position of the rear section of the steering column 6a to change excessively as a secondary collision advances is that the support force from the support brackets 12, 13 is lost as the secondary collision advances.
For example, in the construction illustrated in FIG. 27 to FIG. 29, when the secondary collision advances and the support force from the support bracket 13 on the housing side is lost with respect to the fastening bracket 11 on the vehicle side, the steering column 6a tilts greater than the original angle of inclination as illustrated in FIG. 29 due to the existence of the heavy electric motor 18 that is fastened to and supported by the housing 10. In other words, the rear end section of the steering column 6a displaces upward more than the original position, and likewise the front end section displaces downward more than the original position. Furthermore, when the support force from the support bracket 12 on the column side is lost, the rear end section of the steering column 6a displaces upward even more. As a result, after the support force from both of the support brackets 12, 13 is lost, there is a possibility that the steering wheel 1 will be in a state of being excessively displaced upward, and when that happens, it becomes difficult to operate the steering wheel 1, and even though the vehicle that was in the accident can be moved on its own, this causes handling the vehicle after the accident to troublesome because it is difficult to drive the vehicle from the site of the accident to the side of the road.
In order to stabilize the breaking away of the steering column in the forward direction during a secondary collision, applying the construction disclosed in JP51-121929(U) can be somewhat effective. FIG. 30 to FIG. 32 illustrate the construction disclosed in JP51-121929(U). In the case of this construction, a locking notch 19 is formed in the center section in the width direction of a bracket 11a on the vehicle side that is fastened to and supported by the vehicle body and that does not displace in the forward direction even during a secondary collision, and this locking notch 19 is open on the edge of the front end of the fastening bracket 11a on the vehicle side. Moreover, a support bracket 12a on the column side is such that it is able to displace in the forward direction together with a steering column 6b during a secondary collision.
Furthermore, both the left and right end sections of a locking capsule 20 that is fastened to this support bracket 12a on the column side is locked in the locking notch 19. In other words, locking grooves 21 that are formed on both the left and right side surfaces of the locking capsule 20 engage with the edges on the both the left and right sides of the locking notch 19. Therefore, the portions on both the left and right end sections of the locking capsule 20 that exist on the top side of the locking grooves 21 are positioned on the top side of fastening bracket 11a on the vehicle side on both side sections of the locking notch 19. When the fastening bracket 11a on the vehicle side and the locking capsule 20 are engaged by way of the locking grooves 21 and the edges on both sides of the locking notch 19, locking pins 23 (see FIG. 32) are pressure fitted into locking holes that are formed in positions in these members 11a, 20 that are aligned with each other, joining the members 11a, 20 together. These locking pins 23 are made using a relatively soft material such as an aluminum alloy, synthetic resin or the like that will shear under an impact load that is applied during a secondary collision.
When an impact load is applied during a secondary collision from the steering column 6b to the locking capsule 20 by way of the support bracket 12a on the column side, these locking pins 23 shear. The locking capsule 20 then comes out in the forward direction from the locking notch 19, which allows the steering column 6b to displace in the forward direction together with the steering wheel 1.
In the case of the construction illustrated in FIG. 30 to FIG. 32, the engagement section between the locking capsule 20 that is fastened to the support bracket 12a on the column side and the fastening bracket 11a on the vehicle side is located at only one location in the center section in the width direction. Therefore, tuning for disengaging this engagement section and causing the steering wheel 1 to displace stably in the forward direction during a secondary collision becomes easy.
However, in this construction, in order to more completely protect the driver during a secondary collision, it is desired that the following points be improved. Namely, (1) in this construction the inner edges of the locking notch 19 that is formed on the side of the fastening bracket 11a on the vehicle side come in direct contact with the edges on both the left and right side of the locking capsule 20. During a secondary collision, the locking capsule 20 come out in the forward direction from the locking notch 19 while there is a friction between the inner edges of the locking notch 19 and the edges on both the left and right sides of the locking capsule 20. Therefore, in order for the locking capsule 20 to come out smoothly in the forward direction from the locking notch 19 in order to lessen the impact that is applied to the body of the driver during a secondary collision, it is necessary to keep the friction force that acts between the inner edges of the locking notch 19 and the edges on both the left and right sides of the locking capsule 20 low.
On the other hand, in order to maintain the necessary strength and rigidity, the fastening bracket 11a on the vehicle side is often made of a ferrous metal plate such as a carbon steel plate. Moreover, in regards to the locking capsule 20 as well, in order to sufficiently maintain reliability of the connecting sections with the fastening bracket 11a on the vehicle side and the support bracket 12a on the column side, the locking capsule 20 is often made of a metal material such as a ferrous metal including mild steel or an aluminum alloy. When the material of each part is selected in this way, there is metal contact in the frictional engagement sections between the inner edges of the locking notch 19 and the edges on both the left and right side of the locking capsule 20.
The friction coefficient between metal materials is relatively large, so in a state in which large contact pressure is applied to the frictional engagement sections, there is a possibility that the locking capsule 20 will not come out smoothly in the forward direction from the locking notch 19. For example, when a force is applied at an angle in the forward direction (as shown by arrows α and β in FIG. 4) to the locking capsule 20 due to a collision accident, a large contact pressure is applied to the frictional engagement section between the inner edges of the locking notch 19 and the edges on both the left and right sides of the locking capsule 20. As a result, the load required for the locking capsule 20 to come out in the forward direction from the locking notch 19 becomes large, and so the impact applied to the body of the driver when colliding with the steering wheel is increased by that amount.
(2) In this construction, it is not always possible to sufficiently reduce the break away load, which is the load required to cause the locking capsule 20 to come out in the forward direction from the locking notch 19 and to instantaneously start the forward displacement of the steering column 6b to which the locking capsule 20 is fastened when a secondary collision occurs. This is because, the distance L between the center axis of the steering column 6b, which is the position where the impact load acts, and the engagement section between the locking notch 19 in the fastening bracket 11a on the vehicle side and the locking grooves 21 of the locking capsule 20, which is the portion that breaks away during a secondary collision, is long. In other words, at the instant that a secondary collision occurs, a moment which is proportional to this distance L acts on the engagement section between these locking grooves 21 and the edges on both the left and right sides of the locking notch 19. When this kind of moment act on this engagement section, a force such as to pry open this engagement section acts, and there is a tendency for the friction in this engagement section to become large. This is disadvantageous from the aspect of keeping the break away load low and completely protecting the driver.
Moreover, a long distance L is also connected with an increase in the assembled height of the portion where the locking capsule 20 is located, which is disadvantageous from the aspect of making the steering column support apparatus compact and lightweight.
Furthermore, the locking capsule 20 has a shape in which the locking grooves 21 are provided in the center section in the thickness direction of the surfaces on both the left and right sides, so even when this locking capsule 20 is made using a synthetic resin, or is made using a metal, the processing costs increase. For example, in the case of using a synthetic resin, the injection mold is complex, and in the case using a metal, manufacturing using a simple forging process is difficult.
(3) In this construction, the length in the forward and backward direction of the locking notch 19 and the length in the forward and backward direction of the locking capsule 20 is the same, so as the secondary collision advances, the locking capsule 20 comes completely out from the locking notch 19. Therefore, when the secondary collision has advanced, it is not possible to prevent the steering wheel 1 from displacing excessively in the vertical direction. Therefore, there is room for improvement from the aspect of preventing difficult operation of the steering wheel 1 after an accident.
(4) In this construction, installation holes 24 are formed at a total of four locations, a front and rear location on both the left and right end sections of the fastening bracket 11a on the vehicle side. The fastening bracket 11a on the vehicle side is connected and fastened to a connection bracket 25 using these installation holes 24, and this connection bracket 25 is fastened to and supported by the vehicle body. Therefore, the rigidity of the connection section where the fastening bracket 11a on the vehicle side is fastened to the connection bracket 25 is sufficiently maintained. Moreover, by increasing the locations where this connection bracket 25 is fastened to and supported by the vehicle body, it is also possible to maintain the support rigidity of this connection bracket 25 by the vehicle body.
However, the installation locations for bolts and nuts increases, and thus the number of parts and assembly steps increases. Depending on the conditions of the vehicle body, there is a possibility that maintaining the rigidity of the portion where the connection bracket 25 is assembled to the vehicle body will also become difficult. More specifically, when the dimensions in the forward and backward direction of the installation surface on the vehicle side is limited, it may not be possible to support the connection bracket 25 by the vehicle body at multiple locations separated at intervals in the forward and backward direction, and thus it becomes difficult to maintain the rigidity of the portion where the connection bracket 25 is attached to the vehicle body. Taking this kind of situation into consideration, construction is desired that is able to maintain the support rigidity of the fastening bracket on the vehicle side with respect to this installation surface on the vehicle side, even when the dimension of this installation surface in the forward and backward direction is limited.
As technology related to a steering column support apparatus, an energy absorbing member is disclosed in JP2000-6821(A) that, in order to lessen the impact that is applied to the body of a driver that collides with the steering wheel 1 during a secondary collision, plastically deforms as the steering column 6 displaces in the forward direction together with the steering wheel 1. JP2007-69821(A) and JP2008-100597(A) disclose construction in which the position of the steering wheel 1 can be adjusted, and in order to increase the supporting force for keeping the steering wheel 1 in the adjusted location, a plurality of friction plates are placed overlapping each other to increase the friction surface. However, these documents do not disclose (1) technology for keeping the load required for the locking capsule that is supported by steering column to come out in the forward direction from the locking notch that is provided in the fastening bracket on the vehicle side small; (2) technology for keeping the break away load small; (3) technology for preventing excessive change in the vertical position of the steering wheel as a secondary collision advances; or (4) technology for maintaining support rigidity of the fastening bracket on the vehicle side with respect to an installation surface on the vehicle side even when the dimension in the forward and backward dimension of the installation surface is limited.